1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. One embodiment of the present invention particularly relates to a semiconductor device and a method for manufacturing the semiconductor device.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. An electro-optical device, an image display device (also simply referred to as a display device), a semiconductor circuit, a light-emitting device, a power storage device, a memory device, and an electronic appliance may include a semiconductor device.
2. Description of the Related Art
As semiconductor materials of transistors used for most display devices typified by liquid crystal display devices and light-emitting display devices and most integrated circuits (ICs), silicon semiconductors such as amorphous silicon, single crystal silicon, and polycrystalline silicon are known. Furthermore, as other semiconductor materials, oxide semiconductors have been attracting attention. For example, a technique for applying a transistor in which zinc oxide or In—Ga—Zn-based oxide is used as an oxide semiconductor for a channel, to a display device, is disclosed (Patent Document 1). Furthermore, a technique to apply a transistor in which polycrystalline In—Ga oxide is used as an oxide semiconductor for a channel, to a display device, is disclosed (Non-Patent Document 1).
In addition, to reduce wiring delay due to increase in wiring resistance and parasitic capacitance caused by increase in size and definition of a display device, a technique to form a wiring using a low-resistance material such as copper, aluminum, gold, or silver is considered (Patent Document 2).